Gas separation is useful in many industries and can typically be accomplished by flowing a mixture of gases over an adsorbent material that preferentially adsorbs one or more gas components in a feed stream, while not adsorbing one or more other gas components. The non-adsorbed components are recovered as a separate product. The separation of gas components by adsorption is a conventional technique that is performed in a variety of approaches. For example, adsorptive separations may be based on the differences in equilibrium affinities of the various gas components (e.g., equilibrium separations) or on the differences in adsorption kinetics of the gas components (e.g., kinetics separations).
One particular type of gas separation technology is swing adsorption, such as temperature swing adsorption (TSA), pressure swing adsorption (PSA), partial pressure swing adsorption (PPSA), rapid cycle pressure swing adsorption (RCPSA), rapid cycle partial pressure swing adsorption (RCPPSA), and not limited to but also combinations of the fore mentioned processes, such as pressure and temperature swing adsorption. As an example, PSA processes rely on the phenomenon of certain gas components being more readily adsorbed within the pore structure or free volume of an adsorbent material when the gas component is under pressure. That is, the higher the gas pressure, the greater the amount of readily-adsorbed gas adsorbed. When the pressure is reduced, the adsorbed gas component is released, or desorbed from the adsorbent material.
The swing adsorption processes (e.g., PSA and TSA) may be used to separate gas components of a gas mixture because different gas components tend to fill the micropore of the adsorbent material to different extents. For example, if a gas mixture, such as natural gas, is passed under pressure through an adsorbent bed unit, which may referred to as adsorbent bed unit or vessel, containing an adsorbent material that is more selective towards carbon dioxide than it is for methane, at least a portion of the carbon dioxide is selectively adsorbed by the adsorbent material, and the gas exiting the adsorbent bed unit is enriched in methane. When the adsorbent material reaches the end of its capacity to adsorb carbon dioxide, it is regenerated by reducing the pressure, thereby releasing the adsorbed carbon dioxide. The adsorbent material is then typically purged and repressurized. Then, the adsorbent material is ready for another adsorption cycle.
The swing adsorption processes typically involve adsorbent bed units, which include an adsorbent material disposed within the housing of the adsorbent bed unit. These adsorbent bed units utilize different packing material in the adsorbent bed structures. For example, the adsorbent bed units utilize checker brick, pebble beds or other available packing. As an enhancement, some adsorbent bed units may utilize engineered packing within the adsorbent bed structure. The engineered packing may include a material provided in a specific configuration, such as a honeycomb, ceramic forms or the like. The engineered packing may be formed from the adsorbent material or may be a coating on a structure or support.
Further, various adsorbent bed units may be coupled together with conduits, manifolds and valves to manage the flow of fluids. Orchestrating these adsorbent bed units involves coordinating the cycles for each of the adsorbent bed units with other adsorbent bed units in the system. A complete cycle can vary from seconds to minutes as it transfers a plurality of gaseous streams through one or more of the adsorbent bed units.
However, swing adsorption processes present certain challenges because of several demanding technical factors, such as rapid cycle adsorption processes. These factors may include maintaining a low pressure drop through the adsorbent bed, good flow distribution to and within the adsorbent bed and minimal dispersion (e.g., axial spreading) of the concentration front in the adsorbent bed. Also, another factor may include a rapid cycling time that involves fast acting and low dead-volume valves. Finally, another factor may be that an adsorbent bed unit should be configured to contain the adsorbent bed at certain pressures, to support the fast acting valves, and to minimize the dead volume within the adsorbent bed unit.
These challenges are even more complicated for maintenance of the adsorbent bed unit. A conventional rapid cycle adsorbent bed unit is configured as a vertical cylinder with flat endplates (heads) for minimizing dead volume. Flow enters and exits the adsorbent bed unit through fast-acting valves mounted on the flat heads adjacent to the adsorbent material. The location of the valves on the heads results in significant challenges for the replacement of the adsorbent bed. For example, in a conventional adsorbent bed configuration, the valves on one end of the adsorbent bed have to be removed along with any associated manifolds and/or conduits to provide access to the adsorbent bed. The removal of the valves, manifolds and conduits is labor intensive, time consuming and increases the operating costs of the system. As such, the replacement of the adsorbent bed in the unit is problematic.
Accordingly, there remains a need in the industry for apparatus, methods, and systems that provided enhancements to manage the flow of fluids to the adsorbent beds. The present techniques overcome the drawbacks of conventional swing adsorption approaches by providing access through the head to the adsorbent material within the adsorbent bed unit. The present techniques lessen the maintenance outage, lessen labor and cost associated with the maintenance with the adsorbent bed unit as compared to conventional approaches and systems.